Automatic direction detection for isolated sources of optical radiation such as stars is used in many applications, often in the space environment in which weight and bulk must be kept at a minimum and in which the the presence of radiation and other error sources can present a serious problem. Previous image detectors have utilized an array of charge coupled devices acting as optical sensors and arrayed on a two-dimensional substrate. An image is formed on the substrate that develops a corresponding charge pattern in the charge coupled devices and which may subsequently be clocked off the substrate as a series video signal. The video signal can be applied to a plurality of registers which may be discrete digital components or a line of charge coupled devices themselves.
Typically a plurality of lines of charge coupled devices must be sampled over a substantial number of bits of individual stored signals in order to process the video information for such purposes as detecting the centroid of received image intensity. For this purpose it has been customary in the prior art to use either a long line of charge coupled devices or a plurality of such devices with the video signal fed from the output of one back into the input of the other in order to make accessible at any one instance a number of rows and columns for this signal processing function. It has therefore been common to lead from each charge coupled device in the plural elements a separate electrical lead to an amplifier and subsequent processing electronics so that as each image section passes through the charge coupled devices thus instrumented, the stored signal thereon can be processed and positional information on the stellar image can be determined. Each function requires its own processing electronics and greatly contributes to the bulk of the star sensor system as a whole. In addition, the number of discrete amplifiers and electrical signal leads for each segment in the row and column matrix as well as the distribution of those signals onto diverse charge coupled device elements spreads out the signal for a compact image area into distinct regions which may be subjected to different levels of environmental effects, such as radiation, and therefore contribute a significant error component to the desired signal.